Is it possible to replace front cap on a C to make it a B+?

I would reckon C's are the easiest to sell with the widest market. Just keep on trucking and either sell it as it is, and move on with a good deal, or accept the unit as it is, and be happy.

If you really think a unit that appeals to a small couples group only is what you want and need, then go shopping. You might be surprised at the great deals that can be had from people that bought new or near new, and have a hard time selling that kind of rig.